1. Field of the Invention
This invention is directed to a system for the thermal and/or liquid treatment of edge supported substrates, such as printed electronic circuit boards. More particularly, the invention is directed to a novel lubricant-free chain link conveyor having substrate-supporting pins for suspending the circuit boards or hybrid circuits or similar substrates by their edges in the course of passage through thermal and/or liquid treatment.
In the manufacture of printed circuit boards or hybrid circuits, it is common practice to subject the boards to successive liquid and thermal treatment steps including solvent degreasing, spray coating, drying, baking, and the like. Such treatments are difficult to carry out on a continuous basis utilizing available conveyor systems since the treatments have a deleterious effect on the conveyor systems, as by removing lubricant, baking and solidifying lubricant, and the like. The present invention is directed toward alleviation of the deficiencies of the prior art.
2. The Prior Art
According to current practice, circuit boards are transported through treating chambers by means of full product width wire mesh conveyor belts or roller-type chain conveyors. The successive hubs of a roller chain are provided with projecting pins. Panels to be treated are supported on those pins between a pair of chains and carried through a treating chamber. Such conveyors tend to fail through loss of lubricant in solvent degreasing treatments, by congealing of the lubricant in heating treatments, and the like.